Littérature scientifique sur le sujet « Zancleidae »

The Zancleidae is a hydrozoan family that currently comprises three genera and 42 nominal species. The validity of numerous taxa in this family still needs to be assessed with integrative analyses and complete life cycle descriptions. The vast majority of its species live symbiotically with other organisms, among which cheilostomate bryozoans are the most common hosts. These bryozoan-associated zancleids are host-specific and encompass all species of the genera Halocoryne and Zanclella, as well as several species in the genus Zanclea. Zancleids show variable morphologies, including highly reduced polyps and medusae. Their phylogenetic history is uncertain due to the often intergrading morphologies and the shortage of molecular data. In the present study, two species of Zanclea from the Indian Ocean and the Red Sea are analysed, using morphological and DNA-based approaches. Morphological analyses of the polyp and medusa stages show that, despite a general resemblance with each other and with Zanclella diabolica, the two species differ in some characters, and this is supported also by molecular investigations. The DNA analyses show that the two species are monophyletic and closely related, but divergent from other Zanclea lineages. This newly recovered clade may correspond with the genus Zanclella or with a cryptic genus. The lack of both morphological and molecular data for several zancleid species did not allow to address this issue. Additionally, the single-and multi-locus phylogeny reconstructions reveal that both the family Zancleidae and the genus Zanclea are polyphyletic taxa, since they are composed of at least three divergent lineages. Most zancleid species have polyps and medusae similar to other closely related taxa, and this conserved general morphology poses a challenge in the delimitation of species, genera and even families in this group. Consequently, further conjunct morphological and molecular efforts are strongly needed to clarify the diversity and evolution of the family Zancleida as a whole.

Three species belonging to the genus Zanclea: Zanclea divergens, Zanclea tipis, sp. nov. and Zanclea exposita, sp. nov. have been described as epizoic of bryozoan from the coral reef of the Bunaken Marine Park (Sulawesi Sea, Indonesia). The record of Z. divergens is the second after its description from Papua New Guinea. Zanclea tipis is characterized by a polymorphic colony and a medusa with very extended exumbrellar pouches. Zanclea exposita shows a naked hydrorhiza creeping on the surface of the bryozoan skeleton.An evolutionary trend among the Zancleidae, from species epibionts of algae and bivalve shells with the hydrorhiza covered by perisarc to species symbiotic with bryozoan with a naked hydrorhiza, is discussed.

A new genus and species of hydroid, Zanclella bryozoophila, symbiotic with bryozoans is described. The colony is polymorphic and highly integrated with its bryozoan host. The gastrozooids have one or, rarely, two tentacles; dactylozooids are without tentacles. The medusa stage is reduced to liberable eumedusoids produced on the hydrorhiza, and has exumbrellar nematocyst chambers. The cnidome of both stages consists of stenoteles and macrobasic euryteles. General morphology and cnidome structure place this newly described form in the Zancleidae. A new genus is recognized on the basis of polymorphism of the hydroid and reduction of the medusa stage. The association with the bryozoan is described as commensal. Hydranths appear to feed on particles gathered by ciliary action of the bryozoan lophophore, and the hydrorhiza is surrounded by the bryozoan skeleton. The advantage of this relationship to the bryozoan is believed to be protection, effected by the nematocysts of the hydroid.

Hydroids can establish symbiotic relationships with most marine phyla. Almost entire genera or even families are associated with specific groups (e.g. Hydractiniidae and Cytaeididae with gastropods and hermit crabs, Zancleidae with bryozoans,Dipurenawith sponges,Ralphariawith octocorals,Eugymnantheawith bivalves,ProboscidactylaandTeissierawith serpulids,Bythotiarawith tunicates). Generally, the symbiotic groups belong to the Anthomedusae that, due to the absence of theca, are more plastic in establishing trophic relationships with the hosts. Nevertheless a number of scattered species, mainly Leptomedusae, are strictly associated to algae or sea grasses: in these cases no evident morphological or behavioural adaptations were observed. In animal symbiosis several unrelated symbiotic species show polymorphic colonies or a strong reduction in number and/or size of the tentacles, which are sometimes completely lost. Moreover, these symbiotic species may lack perisarc even in the hydrorhiza.In this paper we summarize the morphological and behavioural adaptations of symbiotic species suggesting that the described aptitude of hydroids to establish relationships with other organisms is not only the result but also the source of the evolutionary radiation of this group.

Green fluorescence is a common phenomenon in marine invertebrates and is caused by green fluorescent proteins. Many hydrozoan species display fluorescence in their polyps and/or medusa stages, and in a few cases patterns of green fluorescence have been demonstrated to differ between closely related species. Hydrozoans are often characterized by the presence of cryptic species, due to the paucity of available morphological diagnostic characters. Zanclea species are not an exception, showing high genetic divergence compared to a uniform morphology. In this work, the presence of green fluorescence and the morpho-molecular diversity of six coral- and bryozoan-associated Zanclea species from the Maldivian coral reefs were investigated. Specifically, the presence of green fluorescence in polyps and newly released medusae was explored, the general morphology, as well as the cnidome and the interaction with the hosts, were characterized, and the 16S rRNA region was sequenced and analyzed. Overall, Zanclea species showed a similar morphology, with little differences in the general morphological features and in the cnidome. Three of the analyzed species did not show any fluorescence in both life stages. Three other Zanclea species, including two coral-associated cryptic species, were distinguished by species-specific fluorescence patterns in the medusae. Altogether, the results confirmed the morphological similarity despite high genetic divergence in Zanclea species and indicated that fluorescence patterns may be a promising tool in further discriminating closely related and cryptic species. Therefore, the assessment of fluorescence at a large scale in the whole Zancleidae family may be useful to shed light on the diversity of this enigmatic taxon.

Gli Zancleida sono una superfamiglia di idrozoi poco studiata ma eterogenea, e presentano una grande varietà di caratteristiche morfologiche ed ecologiche. In questo gruppo di organismi, molte specie hanno storie tassonomiche complesse e confuse, a causa della scarsità di caratteri morfologici informativi, dei pochi dati disponibili sui cicli vitali e dei pochi studi molecolari svolti. Inoltre, molte specie hanno evoluto uno stile di vita simbiotico e vivono in associazioni più o meno strette con sclerattinie, ottocoralli, spugne, briozoi, alghe e molluschi. Con questo lavoro, le tre famiglie simbiotiche Zancleidae, Cladocorynidae e Sphaerocorynidae sono state ampiamente campionate ed analizzate utilizzando tecniche morfologiche e molecolari, al fine di descrivere la loro diversità, distribuzione, ecologia ed evoluzione. Questo approccio integrativo ha permesso di chiarire le relazioni filogenetiche all’interno di ciascuna famiglia, di individuare specie e generi nuovi e criptici, di analizzare le relazioni tra idrozoo e ospite, e di meglio comprendere l’evoluzione di tratti morfologici e preferenze ecologiche peculiari. In particolare, le tecniche di delimitazione di specie hanno rivelato che Zanclea associata a coralli e Pteroclava associata ad ottocoralli sono composte da numerose specie criptiche con diversa preferenza e specificità di ospite e diversa distribuzione. Inoltre, le ricostruzioni degli stati ancestrali di alcuni caratteri hanno mostrato che l’antenato comune alle specie di Zanclea associate a coralli era probabilmente polimorfico, con l’idroriza ricoperta da perisarco e ospite-specifico. L’approccio di tassonomia integrativa ha anche permesso di rivalutare la posizione filogenetica di alcuni taxa, come Zanclea timida, la quale è stata spostata dalla famiglia Zancleidae alla famiglia Cladocorynidae e posizionata nel nuovo genere Pseudozanclea. In maniera simile, sono stati descritti due nuovi generi di Sphaerocorynidae, ovvero Astrocoryne e Sphaerocorynoides, e la tassonomia e sistematica di tutta la famiglia è stata rivisitata e chiarificata. La famiglia Zancleidae è il gruppo più ricco in specie all’interno degli Zancleida, ma le analisi filogenetiche hanno mostrato che questa famiglia, così come due dei generi che la compongono (Zanclea e Halocoryne) sono polifiletici, mentre il genere Zanclella è stato dimostrato essere monofiletico. Inoltre, Zanclea sembra ospitare una diversità criptica in altre specie oltre quelle associate a coralli, come in Zanclea divergens. Infine, è stata presentata un’ipotesi filogenetica aggiornata e ben supportata per l’intera superfamiglia Zancleida e questa ipotesi è stata utilizzata per studiare l’evoluzione di alcuni caratteri morfologici ed ecologici. In molti casi, linee evolutive indipendenti hanno sviluppato strutture simili e, in generale, i caratteri analizzati sembrano essere facilmente persi e riacquisiti durante l’evoluzione. Complessivamente, l’inclusione nelle analisi di specie e generi prima non analizzati e di nuovi marcatori molecolari ha permesso di costruire ipotesi filogenetiche meglio supportate rispetto a studi precedenti e di fare chiarezza sulla storia evolutiva delle tre famiglie analizzate. I risultati ottenuti indicano che questi organismi spesso trascurati ospitano una grande diversità, precedentemente non nota, e sottolineano l’importanza del loro studio e caratterizzazione, in particolare in ecosistemi soggetti a grandi cambiamenti, quali le scogliere coralline.
The Zancleida is a poorly studied yet heterogeneous superfamily of hydrozoans that shows a wide range of morphological and ecological features. Many species in this group have complex and confusing taxonomic histories, due to the paucity of informative morphological characters, the scant available data on their life cycles, and the few molecular studies. Additionally, several species have evolved a symbiotic lifestyle and live in more or less specialised associations with a variety of other organisms, including scleractinian corals, octocorals, sponges, bryozoans, algae, and molluscs. With this work, the three symbiotic families Zancleidae, Cladocorynidae, and Sphaerocorynidae were comprehensively sampled and analysed with both morphology-based and DNA-based techniques, in order to characterise their diversity, distribution, ecology and evolution. This integrative approach allowed to shed light on the phylogenetic relationships within each family, to detect many new and cryptic species and genera, to clarify the hydrozoan-host relationships, and to better understand the evolution of peculiar morphological traits and ecological preferences. Specifically, species delimitation techniques revealed that coral-associated Zanclea and octocoral-associated Pteroclava are composed of several cryptic species with different host preference and specificity and different distribution. Moreover, ancestral state reconstructions revealed that the ancestor of coral-associated Zanclea was likely to be polymorphic, equipped with a perisarc-covered hydrorhiza, and host-specific. The integrative taxonomy approach also allowed to re-evaluate the phylogenetic position of some taxa, such as Zanclea timida, which is here moved from the family Zancleidae to the Cladocorynidae and accommodated to the newly erected genus Pseudozanclea, based on both morphological and molecular data. Similarly, the two new sphaerocorynid genera Astrocoryne and Sphaerocorynoides were described and the taxonomy and systematics of the whole family was clarified. The family Zancleidae is the most speciose group within the Zancleida but phylogenetic analyses revealed that this family, as well as the genera Zanclea and Halocoryne, are polyphyletic, whereas the genus Zanclella was recovered monophyletic. Moreover, Zanclea seems to harbour a cryptic diversity in other species than those associated with corals, such as in Zanclea divergens. Finally, an updated and well-supported phylogenetic hypothesis for the whole Zancleida was presented and used to investigate the evolution of selected morphological and ecological characters. In many cases, independent lineages within this superfamily evolved similar structures and, generally, the analysed characters seem to have been easily lost and regained during the evolution of these organisms. Overall, the inclusion of previously unsampled species and genera, as well as new phylogenetically informative molecular markers, allowed to build more robust phylogenies than in previous studies and to clarify the evolutionary history of the three analysed families. The results indicate that these often overlooked organisms harbour a great, previously unknown diversity and highlight the importance of their characterisation in changing ecosystems such as coral reefs.